The present invention relates generally to panel fasteners, and, more particularly, to panel fasteners adapted to receive a retaining rig.
Many panel fasteners take the form of elongated, cylindrical shafts having external or internal threads for engaging a complimentarily-threaded nut or screw and further having an enlarged head at one end to engage or retain a panel. A common bolt is an example of a fastener.
In a variety of applications, it is advantageous to arrange for the fastener to be retained in relation to the panel. One common approach is to insert the fastener through a hole in the panel and then attach a retaining ring to the fastener's threaded end. The retaining ring prevents the fastener from being extracted, yet still permits a nut to be threaded onto the fastener to secure the panel. The fastener is far less likely to be lost during disassembly and reassembly procedures.
A number of different approaches have been developed for attaching a retaining ring to a fastener. One approach involves forming a plurality of grooves or splines along the length of the fastener to receive inwardly-projecting tabs of the retaining ring. The splines extend fully to the end of the fastener opposite the head. After the retaining ring has been slid onto the fastener, an end cap is attached to the threaded end of the fastener, to close off the channels and prevent the ring from being removed. One disadvantage to this approach is that it cannot be easily or economically applied to hollow, internally threaded fasteners.
In another approach, splines are again formed along the length of the fastener, and a second set of splines is also formed along the fastener, interleaved with the first set. Both ends of each spline in the second set are closed off, so that a retaining ring cannot be longitudinally removed from the fastener when the retaining rings inwardly-directed tabs engage the second set of splines. Crossover slots individually connect the first set of open-end splines with the second set of closed splines. The retaining ring secured to the fastener by sliding its tabs along the open-end slots to the location of the crossover slots, and by then rotating the retaining ring so as to move the tabs over to the closed splines. Extraction of the fastener from the workpiece is prevented as long as the retaining ring tabs do not exit back through the crossover slots and open-end splines.
Although this approach is suitable for internally threaded fasteners, it is nevertheless subject to certain drawbacks. Fastener movement during disassembly procedures sometimes leads to rotation of the retaining ring with respect to the fastener. This rotation can occasionally reposition the retaining ring tabs in the open-end splines, thus permitting inadvertent release of the retaining ring from the fastener. In order to overcome this disadvantage, the cross-over slots are sometimes displaced longitudinally relative to each other so that the ring tabs can be moved from the closed splines to the open-end splines only when the ring is tilted at an extreme angle relative to the fastener shaft. While the likelihood of an inadvertent fastener release is reduced using this latter approach, inadvertent release through random movement of the fastener can still occur.
It should therefore be appreciated that there is a need for a fastener retaining ring combination that does not rely on the orientation of the fastener with respect to a retaining ring to keep the ring attached to the fastener, but that still is suitable for fasteners of both external and internal thread configurations. The present invention fulfills this need.